Apparatus for continuous stretch-blow molding

ABSTRACT

Apparatus for continuously forming molecularly oriented articles generally comprising a multi-station rotary stretch-blow molding machine wherein a plurality of partible blow molds angularly spaced about a continuously rotating support are provided with means for moving the mold sections of said molds between open and closed positions in synchronization with rotation of said support, additional means to longitudinally reciprocate a stretch rod within a cavity of each of said molds and further means for projecting the rod into the cavity and retracting it therefrom, said rod moving means being operable in combination and in synchronization with said mold movements. Another feature of this invention involves means for continuously and simultaneously feeding workpieces to and discharging articles from a stretch-blow mold machine. From a process standpoint, the workpiece, while at molecular orientation temperature, is held temporarily or stored at each moving mold while an article is being formed in the cavity of such mold from a prior preform.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of copending U.S. applicationSer. No. 558,841 and now abandoned, filed Mar. 17, 1975.

This invention relates to method and apparatus for continuously formingmolecularly oriented articles generally comprising a rotary stretch-blowmold machine.

While the blow molding art goes back over one hundred years, it has onlybeen in the last twenty years or so that blow molding of hollow plasticarticles such as containers has achieved significant commercial success.Along with the increased interest in blow molding techniques has comethe strong desirability for improving the strength and other propertiesof finished containers prepared in this manner. Known ways of improvingstrength in plastic containers include changing the chemical structureof the plastic material during synthesis by means of strength impartingmodifiers or increasing the wall thickness of the finished article. Theformer way may undesirably affect other properties of the material whilethe latter could be rather costly.

Another attractive way of improving the strength properties of afinished container involves the molecular orientation of thethermoplastic material being blow molded into the container. Generallyspeaking, molecular orientation of a suitable thermoplastic material isobtained by stretching such material while in the solid state at atermperature just below its crystalline melting point. However, whileorientation can result in a substantial increase in tensile strength itcannot be obtained using a conventional blow molding operation. Onemethod of obtaining the desired oriented product is shown in Wiley etal., U.S. Pat. No. 3,507,005 and involves extruding a hollow parison,cooling it to room temperature, carefully reheating it to just below itscrystalline melting point, grasping the parison at one end whilepinching or clamping it at the other end and stretching itlongitudinally. Then while still held at the first end the parison isenclosed in a mold and blown to conform to the shape thereof. Such aprocess is somewhat complex and does not readily lend itself to the highspeed fabrication which is desired in a successful commercial operation.Another method for preparing oriented containers involves the initialpreparation of an elongated thermoplastic workpiece such as a preformclosed at one end. The preform is then brought to the necessarytemperature and placed in an enclosed mold over a rod which is extendedto stretch said preform after which it is blown using pressurized air toobtain an article having the desired biaxial orientation. While suchmethod represents an attractive way to prepare oriented containers, itmust be carried out in apparatus suitable for high speed fabrication tomake it economical.

Although a large number of blow molding devices suitable for continuoushigh speed production have been disclosed, most are directed to theconventional, non-orientation blow molding process and do not concernthemselves with the method wherein a rod is extended and retracted inthe mold during fabrication of the container.

SUMMARY OF THE INVENTION

Now, there has been developed an apparatus and method capable ofcontinuously forming molecularly oriented articles, said apparatuscomprising a multi-station rotary stretch-blow molding machineparticularly adapted for rapid feeding and discharging from saidmachine.

Accordingly, a principal object of this invention is to provide amulti-station rotary stretch-blow mold machine suitable for continuousoperation.

Another object of this invention is to provide apparatus forcontinuously forming molecularly oriented articles in a rotarystretch-blow machine wherein the movement of the molds and the stretchrod are synchronized with the rotation of a support member.

Another object of this invention is to provide a rotary stretch-blowmachine wherein feeding and discharging is simultaneously carried out ateach mold in combination with the mold and stretch rod moving means tocreate a continuous high speed operation.

A further object of this invention is to provide process improvementsfor increasing the efficiency of a high speed continuous blow moldingsystem by maximizing the mold-closed period during a cycle of operation,while minimizing the complexity of the apparatus system.

Other objects of this invention will in part be obvious and will in partappear herenafter.

These and other objects are accomplished by providing an apparatus forcontinuously forming molecularly oriented articles generally comprisinga plurality of radially partible blow molds disposed at angularintervals on a support mounted on a frame and adapted for continuousrotation about a substantially vertical axis, means for moving the moldsections of said molds between open and closed positions insynchronization with rotation of said support, stretch rod meanspermanently mounted with each mold and operable in combination with saidmold moving means and including rod positioning means for longitudinallyreciprocating a rod while within a cavity of said mold, pressurizedfluid means associated with said rod and a vertical container dischargechute in the vicinity of the cavity of each mold.

In another embodiment of this invention, a stretch-blow mold machinehaving a stretch rod which is reciprocally movable both within the moldcavity and into and out of the cavity is provided with means forsimultaneously feeding a workpiece while discharging a molecularlyoriented blown article.

From a process standpoint, there is provided in the process of blowmolding articles from preforms which includes the steps of positioningsuch preforms within cavities of continuously moving and successivelypresented blow molds, distending the preforms within the moving molds toform the articles and discharging the articles from the still-movingmolds at an eject station prior to charging with additional preforms,the improvement comprising holding or storing a preform temporarily ateach such moving mold while an article is being formed in the cavitytherein from a prior preform.

BRIEF DESCRIPTION OF THE DRAWINGS

In describing the overall invention, reference will be made to theaccompanying drawings wherein:

FIG. 1 is a schematic side elevational view showing one mold station ofthe rotary blow molding machine and incorporating the novel apparatuscomponents of this invention;

FIG. 2 is a schematic plan view showing one mold station of the rotaryblow molding machine;

FIG. 3 is a schematic front elevational view of one mold station of therotary blow molding machine; and

FIGS. 4-11 are partially sectioned elevational side views showing thesequence of operation of one mold station at various times during itsrotation about the rotary support.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referrring now to the drawings, there is illustrated in FIG. 1 a rotaryblow molding machine designated generally as 10 for continuously formingmolecularly oriented articles such as containers and particularlybottles. Only one mold station is shown, however a plurality ofidentical mold stations are equally spaced at intervals around theperiphery of the supporting structure.

Blow mold machine 10 comprises a vertical shaft 12 carrying a hub 14 forcontinuous rotation therewith by conventional drive means such as amotor, gear reducer, or the like, not shown. Fixedly attached to hub 14is a circular mold supporting plate 16.

A plurality of identical mold units generally indicated by the numeral18, only one of which is shown and which will be described hereafter indetail, are equally spaced about the supporting plate 16. Each of themold units 18 comprise partible mold sections 20a and 20b which in theclosed position define cavity 22, the surface of which conforms to theshape of the body of a hollow article such as a bottle to be moldedtherefrom from a thermoplastic material (see FIG. 8). Mold sections 20aand 20b may be conventionally secured (e.g. by bolts or clamps) in moldplatens or carriers 24a and 24b which in turn are operatively associatedwith the remainder of the apparatus in a manner to be describedhereafter in more detail.

Each platen 24a and 24b of partible mold unit 18 is slidably supportedby guide rods 26, 28, 30 and 32 which also maintain the alignment of theplatens and attached molds (see FIG. 3). The four guide rods are fixedlyattached to the supporting structure which is mounted on the supportingplate 16.

Outer mold section 20b and platen 24b is reciprocally moved between openand closed positions by the movement of the rods 34 and 36 (FIG. 2)which are secured to the platen by any conventional means andillustrated e.g. by bolts (FIG. 1). Actuation of mold movement issynchronized with the rotation of the supporting plate 16 through theuse of a scotch yoke assembly, or equivalent, as described below.

As illustrated in FIG. 1 mold opening and closing cam 38 is fixedlyattached to the base of the machine. Cam roller or follower 40 isattached to lever 42 and moves within the contoured slot 44 found in cam38. Lever 42 is connected to shaft 45 through detent (torque limitingdevice) and gear assembly 46. The shaft 45 is connected to a cam oreccentric member 48 and this to a pair of crank or lever arms 50a and b.The lever arms are connected through connecting pin 52 and bearing 53.Lever arm 50b is attached to another cam 54. The bearing 53 is free tomove about the connecting pin and fits into a slot 56 on plate 58 of thescotch yoke assembly (FIG. 2). Tie rods 34 and 36 which are secured tothe outer mold section 20b and platen 24b are fixedly attached to theplate 58 of the scotch yoke assembly and reciprocally move in a lateraldirection with rotation of the shaft 45 through the action of thecomponents described above.

Inner mold section 20a and platen 24a also move with rotation of theshaft 45 but to a lesser degree than the outer mold. This isaccomplished through the interaction of cams 48 and 54 and theirassociated rollers 60 and 62. The rollers are attached to platen 24awhich in turn is supported and reciprocally slides on guide rods 26, 28,30 and 32. The inner mold section 20a is moved through the force ofsprings 26c and 28c positioned on guide rods 26 and 28 respectively(FIG. 1) and those on guide rods 30 and 32 (not shown) which pushagainst platen 24a and the rollers 60 and 62 as cams 48 and 54 move tothe left when the mold is opening.

In synchronization with movement of the mold sections, the stretch rod64 is being moved to the desired operating positions through use of thefollowing means. The stretch rod 64 is moved between its fully extendedposition (FIGS. 4 and 7) and its position just prior to the start of thestretching operation (FIGS. 5 and 6) through the movement of housingmeans such as air cylinder 66 by the action of air cylinder cam 68 andair cylinder cam roller (follower) 70. The stretch rod 64 is affixed tothe air cylinder shaft (not shown) in air cylinder 66 and moves incombination with said air cylinder and shaft. Air cylinder 66 isconnected to cam roller 70 by means of bracket 74. The bracket 74 andair cylinder 66 slide in ways or tracks (not shown) in the supportingstructure or frame designated generally as 77 which is attached torotating support 16. As the support 16 rotates, the air cylinder 66moves in the tracks via interaction with cam roller 70 which moveswithin the slot 72 of cam 68 which is fixedly attached to the non-movingbase of the machine. Cam 68 shown as a box cam travels all the wayaround the rotary machine and depending on the shape or direction of thecontoured slot 72, cam roller 70 and the connected air cylinder 66 andassociated structural components move up and down as desired as thesupport 16 rotates. By this action the stretch rod 64 is raised from thebeginning of the stretch operation (FIG. 6) to its fully extendedposition (FIG. 7).

In the embodiment illustrated, the withdrawal of stretch rod 64 from themold cavity 22, i.e. from its stretch beginning or after blow position(FIG. 6 and 8) to its complete removal from the cavity (FIGS. 9 and 10)is carried out by the application of air to the top side of the piston(not shown) in air cylinder 66. This causes the shaft attached to thepiston and the connected stretch rod 64 to be pushed downward loweringsaid rod into sealing plug 76 as shown in FIGS. 9 and 10. Application ofair pressure is through valve 79 and actuation of this valve is causedthrough interaction of cam 81, fixed to the base of the machine, and camroller 83 connected to the valve by rod or shaft 85. The valve 79 isaffixed to the supporting structure 77 in a conventional manner notshown and rotates with said structure as support 16 to which it isattached is rotated. The cam roller 83 travels along cam 81 completelyaround the machine and by its movement it changes the direction of valve79 causing air to be applied to one side or the other of the piston inthe air cylinder thereby raising or lowering the stretch rod 64. Air isalso being applied when the stretch rod is being moved within the cavityby the interaction of cam 68 and cam roller 70. This air is applied tothe bottom of the piston in air cylinder 66 through air valve 79 andkeeps the stretch rod 64 extended during this part of the cycle. Theactual air supply connections from valve 79 to the air cylinder 66 hasnot been shown so as not to further complicate the drawings and distractfrom the essential features of this invention.

In the embodiment illustrated in FIGS. 7-10, neck jaws 78a and 78b openand close around the neck of the workpiece and blown article through themovement of air cylinders 88 and 90 which are affixed to the moldsections 20a and 20b and platens 24a and b. The respective jaws can befurther moved, for reasons to be described below, by movement of therespective pistons and connected shafts of the air cylinders 88 and 90.Actuation of such movement can be by any of the conventional means, notshown, such as a cam or dog fixed to the base of the machine which tripslimit switches to open or close the air supply valve.

Sealing plug 76 is moved up to seal the neck of the workpiece and thestretch rod when the mold is closed through means of sealing plug cam 80and sealing plug cam roller 82 (FIG. 1). Cam 80 is attached to thenon-moving base of the machine and cam roller 82 travels in an up anddown manner along the cam thereby moving the sealing plug which isattached to it via the action of lever 84 and eccentric member 86 as thesupport 16 rotates. Spring 87 (FIG. 1) holds the plug 76 when it is insealing engagement and thus cam 80 does not have to completely go aroundthe machine and may only be placed in positions where the sealing plug76 is to be lowered. In other words the cam roller 82 can be allowed totravel freely until it again engages the cam 80.

As shown in FIGS. 4-11, means are provided to rapidly feed workpieces 92and discharge blown articles 98 from each stretch-blow mold. A plate 94is affixed to outer mold section 20b and platen 24b and moves in alateral manner along with the movement of such parts through rotation ofsupport 16 and the means described above. The workpiece or preform 92 isdropped into guide means, i.e. a chute or funnel 96 preferably locatedin the vicinity of the cavity of each mold station by a conventionalpick and place device or other means. The vertical chute orworkpiece-holder 96 is supported in a conventional manner, not shown,preferably by support 16 or by some other structure or apparatus andalong with plate 94 provides a means for guiding and retaining theworkpiece 92 until the mold has opened and stretch rod 64 is in positionto receive it and start the sequence for forming an article. At the sametime, a blown article such as bottle 98 is being discharged from themold through opening 100 in support 16, associated with a conventionaldischarge chute, as shown. Alternatively, such discharge opening andchute suppported from support 16 could be upwardly disposed on the axisat cavity 22 to accomodate an upwardly discharging system. The bottle 98is retained in the outer mold section 20b by means of the overlaysection at the top of outer mold 20b and through jaw means i.e., theright neck jaw 78b which has a shape or configuration which surrounds asignificant portion or section of the neck of the bottle 98 (FIG. 10).Thus the bottle moves with the right hand mold 20b and neck jaw 78b.When the bottle is generally over opening 100 (FIG. 11), the neck jaw78b is pushed laterally to the left by actuation of the air cylinder 90and its connecting shaft thereby releasing the bottle from the moldsection of half 20b.

In alternative systems to that just described, for example one whereinthe articles are discharged upwardly from the open mold, cylinder 66 andits associated air circuitry may not be required since it will not benecessary to completely extract rod 64 from the mold cavity with suchsystems. Or, even with such just-described arrangement, it may bepossible via proper cam designs to retract the rod from the cavity viathe mechanical cam-follower system above described.

To put the apparatus in proper perspective and particularly to describethe synchronized action of the respective components, the operation willbe described with particular reference to FIGS. 4-11 which show thesequence of events taking place in one selected mold at different timesas the support 16 is being rotated.

The operation begins as shown in FIG. 4 when a new workpiece 92 such asa previously formed thermoplastic preform which has been reheated toorientation temperature and having a tubular body with one open end andone closed end is dropped onto a fully extended stretch rod 64 and aformed bottle 98 is fully separated from mold section 20b and beginningits descent through discharge opening 100. The preform 92 is free todrop onto the rod extending upwardly on the axis of the mold cavitysince plate 94 has been moved along with mold section 20b and platen 24bthereby clearing the lower end of chute 96 above the now open mold.

In the next step shown in FIG. 5, the bottle 98 is now dropping out ofthe mold cavity into opening 100 and optional chute or funnel 102.During this time the stretch rod 64 holding the newly charged preform 92is retracting (lowering) to its normal start (stretch beginning)position. This is carried out by rotation of support 16 causing camroller 70 to move within the slot 72 to the lower position in cam 68.The air cylinder 66 being affixed to the roller through bracket 74thereby moves in tracks in the frame or supporting structure loweringthe stretch rod 64 and the preform 92 to its position where stretchingbegins. Application of air to the lower side of the piston in aircylinder 66 keeps the stretch rod 64 steady during movement and alsoretains its in the position to which lowered through the action of cam68 and cam roller 70 (see FIG. 1).

As the support 16 continues to rotate, the mold sections 20a and 20b andtheir respective platens 24a and 24b are beginning to close as shown inFIG. 6. This happens through interaction of the mold opening and closingroller 40 in the contoured slot 44 of mold opening and closing cam 38(FIG. 1). The roller 40 moves with rotation of the support 16 causingthe shaft 45 to rotate through the action of connecting lever 42 andthereby causes the scotch yoke assembly and particularly lever arms 50aand 50b to rotate. This action causes the rods 34 and 36 which areconnected thereto to reciprocally move in a lateral direction therebybeginning to close outer platen 24b and its mold section 20b. At thesame time inner mold section 20a is also moving toward a closed positionthrough movement of cams 48 and 54 to the right causing rollers 60 and62 to move in that direction along with platen 24a which is attachedthereto (see FIG. 1). It is to be noted that rotation of the scotch yokeassembly and particularly lever or crank arms 50a and 50b is desirablyslightly greater than 180° to make the mold sections squeeze togetherwhen closed and thereby lock themselves through the added tension orclamping force. Cam 38 does not have to go completely around the machineand may only be placed in sections where opening and closing of the moldis desired.

As the mold sections 20a and 20b close, the neck jaws 78a and 78b alsoclose around the neck of preform 92 through movement of air cylinders 88and 90 which are attached to said mold sections and platens 24a and 24b.At the same time, the sealing plug 76 begins to move up through theaction of sealing cam 80, sealing cam roller 82 and lever 84 as shownalso in FIG. 6.

When the mold sections 20a and 20b reach their fully closed position asshown in FIG. 7, sealing plug 76 moves up to seal the neck of thepreform 92 and the stretch rod 64.

After the mold closing action is complete and the mold cavity 22 fullysealed, the preform is distended from the article. Preferably, thestretch rod 64 begins to raise via movement of cam roller 70 in cam 68through continued rotation of support 16 (see FIG. 1). This actioncauses the tightly held preform 92 to stretch longitudinally as the rod64 approaches and reaches its fully extended position shown in FIG. 7.When the rod is fully extended, pressurized air is provided throughopenings (not shown) in rod 64 via air supply means 65 causing stretchin the radial direction, the preform 92 thus becoming fully stretchedand biaxially oriented. Blow air may alternately be provided through thesealing plug in a manner not shown.

Due to the closing of the mold, plate 94 is returned to its positionbelow chute 96 and a new preform 92a is dropped into the chute byexternal means (not shown) and retained or obstructed in its passage bysaid plate 94. The preform 92a is now ready for feeding to the blow moldstation below (FIG. 7). Holding or storing a preform 92, which has beeninserted in holder 96 from an upstream station, temporarily in suchholder 96 at each moving mold station while an article is being formedin such mold from a prior preform in the manner illustrated increasesthe period during which the mold may remain closed and functioning onthe prior charged preform. In other words, if the preform were to becharged directly to the mold from the prior upstream station, as opposedto merely dropping onto rod 64 from a position already at suchcontinuously moving station, the mold stations would have to remain openlonger during each cycle, and thus for a system of equivalent capacityto that illustrated, additional stations would have to be added, thusincreasing the complexity of the system. Therefore, system efficiency issubstantially increased by loading individual preforms 92 at a chargingstation into holders 96 adjacent to and moving with such molds whilearticles are being formed within such molds from prior preforms. Themolds are then charged directly from such holders, preferably while thepreforms are at molecular orientation temperature, during or afterdischarging articles formed from prior preforms from themolds at theeject station, and while the molds traverse a closed circular path.

After completing the stretching and blowing operation, the stretch rod64 begins to retract through the action of cam roller 70 in cam 68 viacontinued rotation of support 16. The rod then reaches its intermediateposition within the cavity 22 as shown in FIG. 8.

The stretch rod 64 continues to retract until it is free of the moldcavity 22 as shown in FIG. 9. This happens when continued rotation ofsupport 16 causes cam roller 83 to move along cam 81 thereby actuatingvalve 79, allowing air to be applied to the upper side of the pistonhoused in air cylinder 66 pushing the attached rod in a downwardposition. The mechanical and pneumatic retracting actions describedabove may be carried out simultaneously. Simultaneously, sealing plugbegins to retract from its seated position to release the blow air fromthe blown bottle 98. This is actuated through movement of the roller 82along cam 80 in cooperation with lever 84.

The stretch rod 64 and seal plug 76 is now fully retracted and the moldsections 20a and 20b begin to open with continued rotation of support 16through the action of roller 40 and cam 38, reversing the closingoperation described above (see FIG. 10). The formed bottle 98 is carriedalong with the outer mold section 20b and is held there by the shape orconfiguration of the overlay at the top of said section (bottom portionof bottle) plus the configuration of the surrounding neck jaw 78b. Toaid in the movement of the formed bottle 98 with outer mold section 20b,as the mold begins to open neck jaw 78a is moved laterally to the rightagainst the neck of said bottle by action of air cylinder 88 and itsconnecting shaft. This added force helps the outer mold section 20bretain the formed bottle when the mold seal is first broken and therespective mold halves are separating.

As shown in FIG. 11, the outer mold section 20b has now moved intoposition generally above discharge opening 100 in support 16. At thistime, the bottle 98 is now released from its retention by outer moldsection 20b by lateral movement of neck jaw 78b to the left throughactuation of air cylinder 90 causing the neck of the bottle 98 and thebottom thereof (facing up) to move clear of the mold section. At thesame time stretch rod 64 begins to extend itself between the moldsections 20a and 20b through the application of air to the lower side ofthe piston housed in cylinder 66, or alternatively via coaction betweenfollower 70 and cam 68 reversing the retraction procedure describedabove. Alternate means such as forced air means may be provided in outermold 20b to help push the bottle out.

The sequence is complete, when the stretch rod 64 continues to fullyextend itself between the open mold sections 20a and 20b as shown inFIG. 4. This is caused by the movement of cam roller 70 in cam 68through continued rotation of support 16, reversing the proceduredescribed above for retracting the rod. The rod 64 is now in position toreceive a new preform 92 and begin the sequence of operation again.

The embodiments described above show a preferred rotary stretch-blowmolding machine wherein the operation of the blow molds are synchronizedwith movement of the respective stretch rods to provide a facilitycapable of preparing molecularly oriented articles in a rapid continuousmanner thereby saving time and also saving space by the compactness ofthe arranged equipment.

Variations in the equipment, as would be obvious to one of ordinaryskill in the art, may be implemented. For example, the opening andclosing movements of the mold sections may be performed in a moreconventional manner, wherein both mold sections are moved an equalamount. However of course, the advantage of economizing on space aspresented by the preferred embodiment of this invention is particularlystrong when commercial operations are involved. It is further noted thatboth rod positioning means may be actuated by mechanical means such ascams, however, it is considered more practical for commercial operationsto use the preferred combination of mechanical and pneumatic means.While the actuation devices shown are a preferred embodiment, otherconventional electrical, mechanical, fluidic and instrumentation meansmay be used including for example electric timers, solenoids, cams,pneumatic and hydraulic cylinders, switches, etc.

The above description and particularly the drawings are set forth forpurposes of illustration only and are not to be taken in a limitedsense. Various modifications and alterations will be readily suggestedto persons skilled in the art. It is intended, therefore, that theforegoing be considered as exemplary only and that the scope of theinvention be ascertained from the following claims.

What is claimed is:
 1. Apparatus for continuously forming molecularly oriented articles comprising:a. a frame; b. a support on said frame mounted for continuous rotation about a substantially vertical axis; c. a plurality of radially partible blow molds disposed at angular intervals on said support, each mold defining a cavity; d. means for moving said molds between open and closed positions; e. means synchronizing said mold moving means with the rotation of said support; and f. a plurality of stretch rod means, each permanently mounted for operation with an individual mold and operable in combination with said mold moving means and including:i. rod positioning means for longitudinally reciprocating a rod to stretch the workpiece while within said cavity of said mold; and ii. pressurized fluid means associated with said rod for expanding the workpiece into a formed article;said support having a vertical container discharge chute in the vicinity of the cavity of each mold.
 2. The apparatus of claim 1 wherein said rod positioning means comprises:a. housing means for supporting the bottom of said stretch rod and adapted to reciprocally move in combination therewith; b. cam means for longitudinally moving said housing and said stretch rod including a box cam mounted on said frame and a cam roller for movement within a contoured slot of said cam and operatively connected to said housing.
 3. The apparatus of claim 1 including second rod positioning means for projecting said rod into said cavity and extracting it therefrom.
 4. The apparatus of claim 2 including second rod positioning means for projecting said rod into said cavity and extracting it therefrom and comprising valve means for supplying pressurized fluid to either side of a reciprocally movable piston located within said housing, said piston being fixedly attached to said stretch rod and movable therewith, means attached to said frame for actuating said valve upon rotation of said support to supply fluid to the selected side of the piston thereby longitudinally moving the stretch rod.
 5. The apparatus of claim 4 wherein said mold moving means comprise:a. first rod means attached to said frame for slidable supporting and guiding movement of the two mold sections of said partible molds; b. second rod means attached to one of said mold sections and reciprocally movable therewith in a lateral direction; c. means for laterally moving said second rod means including:i. scotch yoke assembly means attached to said second rod means; ii. rotating shaft means for operatively working in engagement with said scotch yoke assembly to provide reciprocal movement to said attached second rod means; iii. cam means for providing rotational movement to said rotary shaft in synchronization with movement of said support and including a box cam affixed to said frame and a cam roller for movement within a contoured slot of said box cam and operatively connected to said shaft by lever means.
 6. The apparatus of claim 5 including means to continuously feed preforms to and discharge articles from said mold and including:i. plate means positioned above said mold for selectively obstructing passage of a preform to said mold cavity, said plate means adapted to reciprocally move in combination with one of said mold sections; ii. guide means associated with said plate means and fixedly positioned above said plate means and the center of said cavity so as to retain a preform on said plate means above the center of said mold cavity when said mold is closed and until said plate means has moved past the center of said cavity clearing the obstruction; iii. means for releasably retaining a formed article in one mold section while said section is moving to open said mold including:a. an overlay section at the top of said mold section and b. jaw means positioned at the bottom of said mold section and surrounding one section of the formed article and adapted to reciprocally move in combination therewith; iv. means associated with said jaw means for reciprocally moving said jaw means in a lateral direction against said article thereby releasing it from said mold section when said mold is open and said mold section is above said discharge opening in said support.
 7. The apparatus of claim 6 including jaw means positioned at the bottom of said second mold section and adapted to reciprocally move in combination therewith, and additional means associated with said jaw means of said second mold section for reciprocally moving said jaw means in a lateral direction against said article as the mold begins to open thereby maintaining said article within the configuration of the first mold section for movement therewith.
 8. A stretch-blow mold apparatus for continuously forming molecularly oriented articles comprising:a. a mold having a pair of partible mold sections disposed on a support and defining a cavity, said support having a discharge opening therein in the vicinity of the cavity of said mold; b. means for moving said mold sections between open and closed positions; c. stretch rod means for said mold operable in combination with said mold sections moving means and including means to move said stretch rod within said cavity and into and out of said cavity; d. pressurized fluid means associated with said rod for expanding a workpiece into a formed article; and e. means to continuously and simultaneously feed preforms to and discharge articles from said mold and including:i. plate means positioned above said mold for selectively obstructing passage of a preform to said mold cavity said plate means adapted to reciprocally move in combination with one of said mold sections; ii. guide means associated with said plate means and fixedly positioned above said plate means and the center of said cavity so as to retain a preform on said plate means above the center of said mold cavity when said mold is closed and until said plate means has moved past the center of said cavity clearing the obstruction; iii. means for releasably retaining a formed article in one mold section while said section is moving to open said mold including:a. an overlay section at the top of said mold section; and b. jaw means positioned at the bottom of said mold section and surrounding one section of the formed article and adapted to reciprocally move in combination therewith; iv. means associated with said jaw means for reciprocally moving said jaw means in a lateral direction against said article thereby releasing it from said mold section when said mold is open and said mold section is above said discharge opening in said support.
 9. The apparatus of claim 8 including jaw means positioned at the bottom of the second mold section and adapted to reciprocally move in combination therewith and additional means associated with said jaw means of said second mold section for reciprocally moving said jaw means in a lateral direction against said article as the mold begins to open thereby maintaining said article within the configuration of the first mold section for movement therewith.
 10. The apparatus of claim 9 wherein said stretch rod moving means include:i. first rod positioning means for longitudinally reciprocating a rod while within a cavity of said mold and ii. second rod positioning means for projecting said rod into said cavity and extracting it therefrom.
 11. The apparatus of claim 1 wherein said support includes a vertical workpiece-holder in the vicinity of the cavity of each mold. 